A standard sheet-metal bending brake has a substantially stationary anvil having a flat and horizontal support surface bounded by and having a straight stationary bending edge and a side surface also bounded by the stationary bending edge and forming an acute angle with the support surface. A plate workpiece to be bent is supported on the surface with an edge region projecting horizontally beyond the stationary edge. A bending assembly displaceable perpendicular to and adjacent the anvil carries a movable bending blade having a movable bending edge parallel to the stationary edge and spaced therefrom in a direction parallel to the support surface and a clamp bar above the support surface adjacent the blade and having a clamp-bar face confronting and substantially parallel to the support surface. This bar is supported on the bending assembly for limited vertical movement relative thereto between a lower position with the bar face below the movable edge and an upper position with the bar face above the movable edge and is normally spring-biased into the lower position. A drive, normally formed by a standard bending press, displaces the assembly with the bar and the blade relative to the anvil between an upper position with the bar face and the movable edge both above the support surface and the workpiece thereon and a lower position with the bar face pressing the workpiece against the support surface and the movable edge below the stationary edge and through an intermediate position with the bar face and the movable edge level with each other and both engaging the workpiece. Thus the bar clamps the workpiece to the anvil and movement from the intermediate position to the lower position of the blade bends over the workpiece edge region.
In such a machine the normally horizontal spacing parallel to the support surface between the two edges must correspond fairly closely to the workpiece thickness for a 90.degree. bend. Ideally the spacing is exactly equal to the workpiece thickness for a perfect such bend. For a different bend angle or thicker workpiece it is necessary to reset the machine in a laborious and complicated manner.